Switch



P. S. BEAR Oct. 11, 1938.

SWITCH Filed Dec. 6, 1935 3 Sheets-Sheet 1 .Z'nz/n $0219:

P. s. BEAR Oct. 11, 1938.

SWITCH 5 Sneets-Shet 5 Filed Dec. 6, 1955 fan 7:4 may Z/mmm Z lQU/D 77L;

Comm/2Y5 Z 01 1/7517 5/00/12 fiu,

Jhwniivm 1 w fiea WW5 "M Patented Oct. 11, 1938 UNITED STATES PATENT OFFICE assignments,

to Bucklen-Bear Laboratories,

Inc., Elkhart, had, a corporation of Indiana Application December 6, 1935, Serial No. 53,146

29 Claims.

This invention relates 'to mercury switches and the like.

The present application is a continuation in part of the co-pending application of Herbert E. Bucklen and myself, Serial No. 665,654, filed April 12, 1933, and my copending application Serial No. 745,842 filed-September 28, 1934.

While I have elected to illustrate my invention in a switch of the metal shell type, there are certain features of my invention which are not limited to this particular type. Also, while the preferred embodiment herein disclosed is a gravity-operated switch, the invention is not limited to that particular mode of operation.

The gravity operated switch, particularly of the mercury type, has long been known. It is attractive in theory because of the theoretical ability to enclose the contacts and the traveling conductor (mercury) in a complete enclosure, where, theoretically, the conditions of operation are maintained even though the exterior be subjected to adverse conditions. Practical attainments fall far short of the ideal, as those skilledin the art well know.

With the theoretically ideal conditions which appear to be possible, such a switch should be capable of an indefinitely long life, i. e. capable I of operating perfectly for an indefinitely great number of operations for an indefinitely long,

time. Practice falls far short of this ideal, as those skilled in the art well know.

Also, theoretically, there should be no limit to the current-carrying ability of such a switch. Again, practice falls far short of the ideal.

Another attractive featureof the enclosed mercury switch is that the making and breaking of the circuit occurs within a complete enclosure, so that the switch, theoretically, is safe to use where an open spark or are would be dangerous because of combustible or explosive materials in proximity to the switch. Here, also, practice falls far short of theory, as it is not at all-unusual for switches of the prior art to explode in operation and thereby, instead of providing a protection, actually constituting a hazard as is known to those skilled in the art.

The general object of the present invention is to produce a mercury switch of the enclosed type which will be superior in structure and performance to known switches.

An important aspect of the present invention is the selection, preparation and coordination of materials and parts to render the working parts of switch stable chemically, mechanically and electrically even under severe duty. In other words I teach herein how to make a switch substantially non-deteriorating from age or use.

One of the specific objects of the invention is to increase the capacity or duty of enclosed mercury switches. crease in current carrying ability of switches is made possible. Also by my invention, a marked increase in the amount of current that can be made and broken is made possible. 7 Another object of my invention is to increase the life of a switch of the present type. By my invention, more operations of making and breaking a given current are made possible.

Another object of this invention is to improve the repeat performance of switches of the present type. By my invention the uniformity of operation of switches of this class is greatly enhanced. My invention makes possible more accurate control of the exact instant that circuit is made or broken and likewise of the exact angular position at which. contact will be made or broken.

Another object of my invention is .to eliminate irregular making and breaking or stuttering" of switches of this class. By my invention the sharpness of make and break is improved and made permanent.

.A'further object of the present invention is to decrease the cost of switches. By my invention, the initial cost of a switch of a specified capacity is low and the life is long as compared to prior switches. As a result, the overall cost to the consumer is greatly reduced.

, Another object of the present invention is to provide a switch of greater strength and ruggedness, both from the standpoint of external injury and from destruction by internal operations. In the switch of my invention, the exposed parts are chiefly strong, metallic parts. The only ex-- posed insulation is a tough, strong piece of -fibrous insulation or the like. The switch is not injured 40 in shipping, even though the amount of mercury be large and the handling rough. This saves both in loss in the factory and in transit, and lowers the cost of packing materially.

A further object is to provide a switch of greater safety. By the use 015 my invention, much greater internal pressures are permissible than with switches of the prior art. The switch of my invention will yield under pressure in a definite manner only. and hence is much safer for the operator or attendant as well as for the adjacent machinery and materials.

A further object of my invention is the provision of a switch which is capable of short time overload demands far in excess of what can be By my invention, a marked in- 5 withstood by switches of the prior art. My switch will stand temporary overloads or a temporary. schedule of operations above normal with-'- out injury, which switches of the prior art could not endure.

A further object of the present invention is to .trode.

A further object of my invention is the provision of improved closure means for the open end of the shell.

The switch of the present invention makes pos sible the employment of switches of the enclosed mercury contactor type in fields and for services now closed to such switches because of their limitation as now constructed.

Now, in order to acquaint those skilled in the art with the manner of constructing and operat-.,

ing a specific iorm of the invention, I shall describe in detail an embodiment thereof in the following specification in conjunction with the accompanying drawings.

I have provided a switch in which the making and breaking of contact is effected over the ceramic surface which spaces the two electrodes apart. In this connection, I avoid any p ssibility critical size of mercury globule is capable of retaining individual stability throughout the entire working angie of operation of the switch. The

length of the body of mercury that will have inherent stability I have found to be of the order of twice the length of a meniscus curve, that is, considering a body of mercury having curved meniscii at opposite ends, the stability is determined bythese ends, since the intermediate portion of the mercury .gives no stability. The length of a meniscus curve I define as the longitudinal distance from the point of curvature of the meniaus downwardly from the top surface of the mercury to a plane tangent tn the. endof the body of the mercury. By making the body of mercury ef a length equal to twice this distance, I retain the stabilizing characteristics of the meniscii-whiie at the same time eliminating the unstable portions Although stability will be retained with a body of mercury of iess length, it will not give the desired electrical conductivity for heavy loads, since the cross-sectional'area of mercury available for current carrying purposes will be smaller than is desirable. I have found the desired length for stability to be not, more than By initial purification of the mercury in accordance with the method disclosed and claimed in my copending application, Serial No. 67,816, filed 1 freed of injurious impurities to an extent not heretofore attained in the art. This mercury so among which arez-freedom from a dry surface film which interferes with making contact with the fixed electrodes and with making mercury to mercury contact; high surface tension, winch allows maximum height of the meniscus and therefore greater cross-section of mercury when mercnry to mercury contact is formed; high conductivity; and long life without change of the above characteristics, even though subjected to heavy duty and high temperature. As an insur ance of the initial purity of the mercury I provide a fractional fill of anhydrous triethanolamine which covers the surface of the mercury at all times. If desired, an atmosphere of hydrogen may be provided above the liquid, but this is not essential. A vapor fill of triethanolamine is entirely satisfactory, since the triethanolamine appears to provide the necessary chemical protection against filming, oxidation, or acid forming within the switch. it appears to unite with any free oxygen within the casing and thus protect the mercury from oxidation or any other deterioration in use.

Another important advantage attained by my present switch is the provision of a tough, electrically puncturable, mobile liquid film that is present-over the interior surfaces of the switch envelope and over the mercury contactor. I have found that an anhydrous alkaline film is most suitable for this purpose, since the alkalinity preserves the full surface tension of the mercury whereby the body of mercury will always stand at its full meniscus height, approximately 3 millimeters, and will not flatten out, as is the case when in the presence of an acid. The film acts as a lubricant for assisting movement of the mer cury- Further, the anhydrous characteristics of the film preserve the metal surfaces and mercury against oxidation caused by moisture within the switch envelope, and against the deleterious effects of any occluded gases. However, the film is most effective in assisting the operation of the switch by reason of its efiect during making and breaking of the circuit between the two iaodies of mercury. The filmcovering the stationary or stable body of mercury,- upon approach of the moving body,.merges with the film' covering the moving body. This film thereby extends between the two'b'odies of mercury, and retards their approach into contactgbuilding'up the cross-sectional area of mercury at the contacting surface by this resistance. Then, as the mass or inertia of the moving body of mercury increases the pressure on the film, tending to squeeze the fihn out from between the two bodies, the eiectrical potential suddenly punctures the film, and the mercury rushes into contacting engagement along a contact area that is considerably increased over the res. that would normally be present. This prevents sputtering er frying of the contacting faces of the mercury and insures a sudden and complete closure c-f contact through a relatively thick section of mercury capabieof carrying the current with, a resistance. sufiiciently volatile so that a portion thereof va- The film is' porizes upon contact and dissipates heat readily to all parts'of the switch. The vaporization also effects a continuous purging of all internal surfaces of the switch, and serves to prevent notation of scum or foreign particles on the adjacent con- 7 tacting portions of mercury. March 9, 1936, I provide mercury which is Another advantage of this film empioyed in combination with a stable body of mercury which stands above the sharp cutting edge is that it prevents arcing across this edge, thus preserving the ceramic or refractory material forming the spillway and cutting edge. The high meniscus and the presence of the liquid cooperate in the protection of this edge.

The film also forms immediately over the separating bodies of mercury upon breaking of contact therebetween, and acts as an arc extinguisher for preventing drawing of an arc between the relatively moving bodies as they snap away from each other due to surface tension.

Prior types of switches employing mercury contactors have attempted to use alcohol as a liquid fill. However, alcohols and similar compounds of this class cause mercury to separate into'fine globules that reunite with great difficulty. The same disadvantages arise with the use of oils, kerosene and the like. This is also true with water to a marked degree, althoughv I have found that the addition of a slight amount of ammonia will overcome this characteristic by rendering the fill alkaline. When mercury has been shaken up in contact with oils or the like it separates into fine globules and tends to remain in such condition over long periods of time and difllculty is encountered in getting them to reunite, usually necessitating centrifugal force or a solvent to remove the oil or kerosene.

The high viscosity oftriethanolamine allows the mercury to break up into globules, but they reunite in one mass again almost instantaneously due to the alkalinity of the film. Such action is ideal for mercury'switches, because if the mercury becomes broken up by jarring or rough handling, the main body and the retained body will have returned to their proper shapes in the time required to mount the switch in a clip and v connect the conductors to an external circuit.

Other objects and advantages of the present construction willbe explained in conjunction with the following detailed description of my switch which, taken in conjunction with the accompanying drawings, will disclose to those skilled in the art the particular construction and operation of a preferred form of the present invention.

In the drawings:

Figure l is a sectional view through one form of the switch;

Figure 2 is a transverse sectional view taken substantially on line 2--2 of Figure 1;

igure 1 with the application of an enclosing seal hereto;

Figure 4 is a transverse sectional view taken on line 4-4 of Figures;

Figure 5 is a view similar to Figure 3, showing the switch in closed position;

Figure 6 is a diagrammatic view of a modified type of switch;

Figure 7 shows the switch of Figure 6 in switch-closed position;

Figure 8 is a partial diagrammatic enlarged view of the bodies of mercury at the instant prior to contact;

Figure 9 is a diagrammatic illustration of the determination of a stable body of mercury;

Figure 10 is a diagram illustrating the tendency of the two bodies of mercury to pile up vertically before breaking the intervening film and merging;

Figure 11 is a similar diagram illustrating the condition of the mercury at the instant of merging the two bodies; v D

Figure 12-isa longitudinal sectional view of a Figure 3 is a sectional view of the switch of commercial embodiment of our invention;

Figure 13 is a diagram illustrating the making Figure 15 is a longitudinal section of a modified form of switch;

Figure 16 is a cross-section taken on line l6--l6 of Figure 15;

Figure 17 is a longitudinal section of a low angle modified type of switch;

Figure 18 is a cross-section taken on line |8-l8 of Figure 17 and Figures 19 and 20, respectively, are fragmentary sectional views showing two modifications of the inner electrode of the switch of Figure 1'7.

Referring now in more detail to the drawings, in Figure 1 I have disclosed a switch comprising a drawn metal shell 5, forming the main portion of the switch envelope. The shell may be formed of substantially pure iron, stainless steel, or other ferrous material whichis not attacked by mercury. The open end of the shell 5 receives the inwardly extending flange 6 or a ceramic spacing member I, which at its opposite end is provided with the flange 8 receiving the second electrode shell or cap 9. This ceramic is preferably porcelain. It may be wet process porcelain, isolantite, or other refractory insulation. If wet process porcelain is used no glazing is necessary.

Intermediate the flanges 6 and 8 the ceramic I is provided with an axially extending tapered bore III, which bore, at its small end, is terminated by the radially extending wall I2. The

bore II) is smooth. The dihedral or solid included angle is less than The corner 22 is sharp.

The shells 5 and 9 may be secured to the ceramic l in any suitable manner, as by cement, threads, or in the manner disclosed in the previously mentioned copending applications. The shells 5 and 9 may have flanges welded thereto, and these flanges clamped or beaded together in insulated relation. Ears may be attached to the shells and these cars held together by screws, rivets or the like, suitably insulated. The particular manner of securing these members 5 and 9 together in this embodiment may be widely varied within my invention. The shell 5 is pro- .vided with a contact lug l3 suitably secured thereto at one end and receiving the conductor [4 at the other end for connecting the shell to one side of the circuit controlled by the switch. The shell 9 is similarly provided with a lug l5 receiving the conductor 16 connected to the other side of the circuit. v

V The housing is assembled and mechanically secured together, leaving only the filling opening in boss 20.

Suflice it to say that I clean the inside surface with triethanolamine before evacuation. Evacuation to remove oxygen is then carried to a fairly high value. The interior may be washed with hydrogen and again evacuated. After final evacuation the desired amount of cleaned mercury is introdubed. Thereafter the desired amount of liquidfill is introduced, by a following atmosphere of hydrogen or a hydrocarbon gas or the like, and the envelope is sealed off.

The mercury employed in my switch is especially-prepared for the service which it must perform, by the method disclosed and claimed in my copending application, Serial No. 67,816 filed March 9, 1936; Sufiice it to say that I charge a relatively large amount of distilled, cleaned, and neutralized mercury, (for example, 30 cc.) into a closed chamber which is in reality a large mercury switch. That is to say, it comprises an iron shell electrically divided by a refractory insulator passage of current, imparts certain characteristics to the merucy which are of great importance in the performance of the switch.

First, the mercury so treated has a very positive and high meniscus. This isimportant in several respects, namely, first, in the increased cross-section of mercury to mercury contact in making qircuit, second, the' greater snap in breaking circuit, and third, the higher the meniscus the less angle required to cause it to travel on va supporting surface.

Second, the treated mercury appears to have a skin that protects it from oxidation, even if exposed for some time to atmosphere. This skin appears to be a thin film of' triethanolamine. This film lubricates the mercury and, makes gravity travel easier, also-lowering the angle required to cause it to travel.

Third, the switch containing mercury so treated runs cooler on a test run than will a like switch with the mercury cleaned only as known by the prior art.

Fourth, the interior of the. switch remains cleaner and operation is sharper and at a lower angle, both because of the permanent character of the cleaned parts and for the reasons above given.

Fifth, the life of the switch on destructive tests, using mercury cleaned as per my method, is vastly increased.

The amount of mercury employed in my switch is proportioned to be ample to form the desired conducting link between, shells 5 and 9. In a" 35 ampere switchI employ about 6 cc. of mercury. The liquid fill in that size switch is about cc. of triethanolamine.

, and the ceramic I are so porportioned as to give the desired cross-section of mercury for conductivity. The shell 5 retains, back of shoulder l2, a sufiicient body of mercury to provide adequate contact conductivity with the shell and to provide a substantially stable body of mercury back vmeniscus curves of of shoulder 22 standing at maximum meniscus height. The shell 5 should be long enough to provide the free runway room to let the parted body of mercury travel endwise without piling up.

By the provision of the radially extending wall l2, there is provided an acute angle shoulder or edge, indicated at '22 between the tapered passageway l andthewall [2, which prcvidesasharp. cutting edge over which the mercury is parted for breaking of contact, and over which the mercury contacts during contacting engagement. i

Bysuitable spacing of the end wall portion 23 of the shell 9 with respect to this radially extending ,wall l2 of the ceramic 1, I provide for introducing a. stable body of mercury into the bottom part of annular recess defined by the wall l2 and the end wall portion 23 of the shell 9. This stable body of mercuryshould, for optimum conditions, be of the order of the length of two mercury, which curves are .determined as illustrated in Figure 9.

I have found that a body of mercury retains The shells and 9 it stability due to the cohesion effect provided by the surface tension at the defining edge of the body, of mercury. In Figure 9 I have disclosed a body of mercury 25 lying on a flat surface 26, and it will be noted that the end portions thereof assume definite meniscus curves indicated at 21 and 28. The length of such a meniscus curve is considered to be the distance from the point at which the curve initially starts from the top planar surface of the body of mercury, to a plane extending tangent to the end of the mercury, this distance being indicated by a in Figure 9. The portion of mercury between these end portions, indicated at b in Figure 9, is unstable, and is not subjected to the cohesion effect which imparts stability to the end portions 21 and 28.

By thus eliminating the portion of mercury within the space b, I provide a stableglobule ofmercury comprising the portions 21 and 2 8 which are joined to form a. globule that possesses inherent stability in all operating posi-- tions of the switch. I have found that by disposing two vertical end walls a distance apart equal to- 2a in Figure 9, the entire top surface of the included body of mercury, nomatter how deep, will provide the maximum height of meniscus above the points of end tangency, i. e., contact with the vertical end walls, and a high degree of stability for any required motion or inclination utilized in operating the switch. This is of great importance in securing the desired uniformity of response which is termed .repeat performance". The body of mercury I8 is preferably held in this manner, the spacing between the radial wall l2 and the end portion 23 of the shell 9 being such as to produce a globule of mercury which is of the order of the length ,of two meniscus curves, which is approximately equivalent to of an inch.

While I have shown in Figures 1 to 5 the length of the body of mercury was greater than the dimension stated, these drawings are not to scale meniscus high above the defining shoulder 22,

producing a globule of mercury which has a relatively large surface available for contact by the approaching edge of the body of mercury I! when the'switch is moved toward switch closed position. f I

By providing an acute angle cutting edge or shoulder 22, with the tapered spillway l0 extending directly from this edge downwardly to the other electrode, I produce a. switch which has the decidedly'advantageous feature of "repeat performance". By this I mean that the switch,

opens the circuit at a certain angle of inclina- I tion during successive switch opening movements,

and likewise closes the circuit at a certain predetermined angle of inclination during successive switch'closing movement, even under wide variation or the rate of tilting. This insures that any control circuit connected to the switch will be operated at the same point or angular position of the switch at all times, and, consequently, a switch which is adapted to cut in a circuit at a predetermined point will always out in the circuit at this same point, depending upon the differential range covered with respect to the operating angle of the switch. By the provision of the sloping surface extending directly from the shoulder at 22 downwardly into the other electrode, the weight of the overhanging portion of mercury as the switch moves toward open switch position insures that severance of the two bodies of mercury will occur at this shoulder, which is the point of smallest cross-sectional area, thus insuring that the globule of mercury 18 will remain the same after each successive switch opening operation. This is also efiected by reason of the inherent stability of this globule of mercury as determined by the spacing between the radial wall I! andthe end wall 23 of the shell 9.

Thus, a switch constructed in this manner is capable of producing repeat operation at the same angle of inclination, whether'tiltlng be rapid or very slow, and in which the circuit closing and circuit opening contacts are all made at a certain predetermined point in the switch, with no possibility of overhang or sputtering, and no possibility of additional small particles of mercury running down the inclined surface due to breaking of the circuit somewhere along this surface, which might cause a flickering operation. This, in effect, produces a switch which has a very positive and reliable action, and is accurate in operation with respect to predetermined response to either temperature, humidity, or other conditions, or for use with mechanical or electro-mechanical movements of calibrated instruments -and the like. I

For accurate repeat performance the mercury must be broken in such a manner as to leave a definite, uniform and stable retained body at each operation. For this purpose the conical surface It should directly intersect the surface of the wall l2, which is preferably, but not necessarily, a plane at right angles to the axis of the bore III. The angle of the incline formed by the surface of bore III with the horizontal axis thereof is low enough to hold the mercury thereupon by the surface tension of the mercury, so as to give it a definite snap action on breaking, and thereafter a definite travel'or run substantially as a free body. This angle may be of the order of between 1 to 12 and 1 to 20.

In Flames 13 and 14 I have illustrated the manner in which contact is made and broken when the inclined surface A of the ceramic B does not intersect the wall C which defines one side of the mercury pocket but leads to and intersects a cylindrical wall D that intersects surface C. In this construction, tilting of the switch as indicated by the arrow in Figure 14 causes the mercury to be attenuated between the mercury pocket and the inclined wall. The point of greatest attenuation is on the line E, which is the junction of surfaces A and D. But this point of maximum attenuation is not so sharp and decisive as desired, and breaking of the body of mercury may occur anywhere along the surface I) with a piece of mercury resting upon the surface D in unstable position and condition. Also, depending upon the speed of tilting, the point of breaking will vary and no two operations of breaking are alike. If the break is slow, rupture,

of the mercury will tend to occur on the ridge or line E, leaving a small body of mercury on tilting occurs, this small body of mercury may run ofl! the shelf and in doing so may momentarily reestablish the circuit, causing mis-operation. If the motion of tilting is more rapid, the rupture of the mercury may occur further back than ridge E. There is no definite predictable action. Hence, when the circuit is again to be established, the angular position at which the two bodies of mercury meet is not accurately definable, as it will vary.

Figure 13 shows the difiiculty encountered in closing circuit under these conditions. If the advancing body of mercury H is caused to move forward slowly, a part J may run over the ridge E and momentarily close the circuit and then part at the ridge'E and open circuit until the main body H closes the gap and again closes the circuit. Also, if the body retained in the pocket has a small overhanging portion lying on surface E the angular position at which closure will occur will vary and sharp, accurate operation of the switch cannot be assured.

The heating caused by closure and opening of the circuit by such a switch is excessive because of the unnecessary attenuation and unnecessary arcing produced by the device.

The switch shown in Figures 3, 4 and is similar to the switch shown in Figure 1, except for the application of asealing coating indicated at 29, formed of a suitable compound, such as "Bakelite, cellulose acetate or the like, which completely encloses the switch envelope and seals the same. This provides a more or less resilient coating capable of absorbing impacts and the like, preventing damage to the interior of the switch due to dropping of the switch or the like, and in addition provides an insulating surface which may be attractively finished for advertising purposes or-the like. The characteristics of a relatively stable body of mercury I 8 and a sharp cutting edge on the insulating surface over which contact is made and broken is embodied in this switch, and no further description thereof is belie'ved necessary. The construction and mode of operation is essentially the same as that of Figure 1.

With respect to the switch shown diagrammatically in Figures 6 and 7, this switch provides a drawn steel shell or the like indicated at 30, which at its open end is joined in any desired manner to a ccaxially extending ceramic insert or the like indicated at 32, which ceramic is closed at its open end by a second steel electrode or other suitable electrode such as a cap or plate 33. The electrodes 30 and 33 are connected to any suitable source of current supply. It is obvious that the electrode 33 need not be of the particular diameter shown, nor be formed as a disc, within the purview of the present invention. It maybe set into the ceramic or it may be in the form of a. cup, as shown in Figs. and 11, abuttingthe end of the ceramic to define the mercury pocket.

The body of mercury indicated at 34 is trapped between the substantially radially extending wall 35 terminating the tapered spillway surface 36 which extends longitudinally of the ceramic 32, and the spaced wall or surface of the electrode 33. The spacing between the walls 33 and 35 is of the order of J; of an inch, and insures that the body of mercury trapped therebetween in the annular groove defined by these-walls and by the extending flange portion 31 of the ceramic will inherent stability tending to retain the shelf formed by surface E. Then, as further less length than thatfiindicated, but then the; maximum-height of the mercury will not be attained. r

This construction insures that the same quan- 'tity of mercury will iremain in'the 'groove or pocket at all .times, and thus the same angle of tilting will invariably cause the body of mercury 38, whichis in contact with the electrode 30, to come into contact with the body of mercury If this spacing exceeds the length of two meniscus curves, aspreviously pointed out, the body of mercury will be unstable and upon switch opening movement, either rapid or slow, more or less mercury, respectively, may leave the groove 34 and run down the, surface 36.' In such case, upon reclosing of the switch, a greater or smaller angle of inclination may be necessary, depending upon the volume of mercury trapped against ihe electrode 35. Thus the switch will not open and close the circuit invariably in response to a cer tain inclination, as is desired for repeat performance, and consequently the switch cannot be used for accurate control, purposes. By the provision of a surface which slopes immediately from the sharp cutting edge defined by the junction of the surfaces 35 and 36, no tendency of the mercury to break anywhere along this surface will be provided, since the thinnest section of mercury, during switch opening movement, will always be at this shoulder, and consequently the rnercurywill break at this point before any possibility of its breaking at any otherpoint is presented. Thus the making and breaking of circuit will always occur over this shoulder, and since the volume of mercury ,3; remains substantially the, same at all times, it will maintain a certain constant surface area which can be contacted by the approaching edge of the mercury 38, and which will be engaged by the approaching edge of the mercury 35 only upon a predetermined inclination of the switch. For this reason the switch gives positive repeat performance, .and thus can be employed under the most sensitive conditions met with in calibrated instruments, and other mechanical and electige mechanical motions.

In Figure 8 I have shown diagrammatically the manner in which an .increased surface. cgntact' between the two bodies of mercury may be attained iniorder to insure a sufilcientcross-sectional area of mercury for earring heavy cur--v rents required by certain circuits which may be controlled by the present i type of switch.

I have found ethat cetain insulating liquids possess characteristics which render them highly desirable for use in switches of this character. One desirable characteristic is that they preserve,

cury in order that it may stand at its full Yrnem'scus height. These liquids are peuliarly'effective in lubricatingthe internal surface of the switch envelope to facilitate me vement of the mercury therealong, and also cieansing and maintaining clean the internal surfaces of the switch to keep them free from scum, foreign particles and g the like, which are floated or absorbed into this i i of the arc to all portions of the switchfenvelcpe.

liquid. 7

H I have employed ethyl alcohol, castor Tl, glyc- :erine, and triethanolamine for' this purpose. I find that alcohol, castor oil and glycerine have cerain characteristics rendering them advantageous for use ina mercury switch, but they allow formation of gipbules which are difiicult to reunite. I have found triethanolamine preferable.

lies; over the surface of the mercury. As 'this dust is not a conductor, any appreciable amount of it will prevent good clean mercury 'eontact. By introducing clean mercury (exide free) treated as aforesaid into an envelopetj liat has been cleaned of everything but the atmosphere, then by evacuation removing mos; of this atmosphere, there is left a slight amount of oxygen. By action of the triethanolaliniine in the presence of an arc, this oxygen is combined with triethanolamine; and forms an alcohol, which is in a gaseous form and the triethanolamin e is changed toward a diethanolamine'. This prevents the deposit of any dust or granular, noncondncting material on the surface of the mercury, eaving substantially a chemically cleans urface. v

I ing the switch of substantially uniform temperature and relativeiy cool. In addition,'th'e liquid possessesarc extinguishingcharacteristics and in the form 'of a'film is electrically puncturable in Eirder that the potentialacross the two bddies of mercury will puncture the film to; allow the-contacting of these two bodies of mercury for completing the circuit. T i

As a result of my -investigation, I have .found that triethanolafrnine seijves admirably for this purpose,;being an anhydrous alkaline liquid which increases or promotes the surface tension char-" acteristi'cs of themercury, facilitates movement of unercury' upon metallic surfaces, and because of jits absorptive characteristics with respect to 'fwater. The combination of hydrogen and oxygen' Qwithin the switch during arcing may form a cer 'tain amount of water which would be injurious to the metallic surfaces within the switch. This combination of' the oxygen with the liquid is es= pecially advantageous in that during filling of the switch there may beoccluded gases containing oxygen within the switch envelope which are not removed by evacuation, and which w'culd have a deleterious effect upon the interior of the switch to a large extent, the surface tension of the merj if permitted to act upon the ferrous surfaces, or the mercury. 7

I have also found that triethanolamine is especially adapted for myf purpose in that it is readily puncturable when placed under pressure be- 'tween two approaching bodies of mercury, and upon, the contact between these bodies of mercury, any arcing or sparking therebetween wiil serve to volatilize the film and dissipate the heat In addition, the film prevents; a relatively thin sliver of mercury running ovef the sharp cutting edge and producing an arc with the stable body of mercury, which arcs would tend to break down and destroy this cutting edge. By the provision of the film, all arcs are kept away from the ceramic edge, and by reason of the relatively large 34. This stable body 34 is but slightly distorted by gravity and standswell above the breaking edge 22. Thetough film of triethanolamine 42 or other similar liquid adheres to the surface of the mercury and is not easily pushed aside or squeezed out. is applied the film will continue to hold as the two edges of the adjacent bodies of mercury fiatteri each other, as indicated in exaggerated form in Figure 10, squeezing the film between them as indicated at 39. The moment the film is broken the two bodies of mercury promptly merge, as indicated at 40, and thereupon the two bodies equalize and the surface of the mercury then levels itself as indicated in Figure '7. It is to be observed that the electrode 33 shown in Figures 10 and 11 is in the form of a cup for defining with the ceramic 32 the retaining pocket or groove for the body 34. Such an arrangement of electrode 33 provides greater area of contact between the body of mercury 34 and electrode 33.

Even when normal potential is applied the tendency is for the film to hold the two mercury bodies apart, each with a high meniscus, until the film punctures and allows the two bodies to merge, with ample conductivity. The tough alkaline film provided by the triethanolamine, which, even in the presence of oxygen and the electric arc remains alkaline and protects the metal parts, and saves the sharp edge of the ceramic from injury by the arc, is an important feature. The heat dissipating character and the pressure limiting character of the limited liquid fill is of importance.

In Figure 12 I have illustrated, on a slightly enlarged scale, a form of heavy current switch suitable for heavy duty. This switch is rated at 35 amperes and will stand, on a resistance load, more thanv double the rated amperage indefinitely without undue temperature rise. On a lamp load (tungsten lamps) the initial rush of current is about times running load. Motor loads draw (in 200 watt lamps) without failure or undue tem- 1 perature rise.

The switch is provided with a two-diameter tubular iron shell 45 having the smaller closed tubular portion 46, theenlarged diameter portion 41, and the joining conical portion 48. The shell and electrode are made preferably of substantially pureiron. The shell may be made by drawing or spinning, or it may be built'up by welding, or in any preferred manner. A ceramic 49 of generally tubular form-has a conical bore 50 terminating in a sharpannular shoulder 54. A counterbore of cylindrical form terminating in the radially extending annular shoulder v52 is formed in the right hand end of the ceramic as viewedin Figure 12. The iron electrode 55 hasa short cylindrical extension 55 which extends into the counterbore to. define the back wall of the mercury retaining groove or pocket 51 containing If no potential to break the filmv the stable body of mercury 58. The electrode 55 has a stem 59 the .outer end of which is threaded to receive nut 50. A suitable body of mercury 62 is adapted to travel into and out of engage-.

ment with the stationary body 58 to make and break circuit as the switch is tilted alternately one way, then the other. v The-ceramic 49 has an outer cylindrical portion 53 of substantially less diameter than the inside diameter of the enlarged portion 41 of shell 45. The left hand or forward end of the ceramic has a tapered'shoulder 54 extending to a blunt taper at 63 which is substantially parallel to the conical portion 48 of the shell.

The ceramic 49 and the electrode 55 are enclosed in a soft, tough cup or envelope 64 of rubber or a synthetic rubber substitute, having a cylindrical portion 65, a flange 66, and a bottom or back 51. This bottom or back 51 is perforated to pass or receive the stem 59. A plate of insulation,

58, preferably formed of Micarta or canvas impregnated with a synthetic resin such as Bakelite" overlies the bottom or back 61 of the rubber cup 64. tively stiff but is also tough and will gradually deform under excessive pressure and heat, but will not shatter. It fits quite snugly in the bore of the enlarged portion 41 of the shell. It is backed up by a steel retaining ring 59 having an internal diameter less than the diameter of the electrode 55, whereby it overhangs the periphery of the electrode when compressed into position. The edge of the shell as at 10 is beaded over the ring to compress "the rubber cup or envelope 64. The pressure of the plate 68 is transmitted directly to the back or bottom of the rubber cup. This does two things; first, it forces the electrode 55 against the ceramic 49, pushing it against the flange 66, which flange is compressed between the tapered shoulder 54 of the ceramic and the tapered wall 49 of the housing. Second, the pressure tends to flow the rubber into firm engagement with the This washer or plate 68 is rela-.

cylindrical surface 53 of the ceramic and the containing wall of enlargement 41. The rubber is like a viscous liquid, substantially incompressible and tending, under pressure, to flow into any cavity. As a result the assembly is liquid and gas tight, even under great internal pressures running as high as 1000 lbs. per square inch.

The nut 50 and the washer under it are prefer ably drawn against the insulating plate 69, further holding the parts together in more rigid fashion, particularly serving, by the stiffness of the electrode 55, to keep the plate 58 from bulging out at the center. If desired, the stem 59 may be made hollow so as to permit beading the edges over the washer to serve as a fixed assembly before or after insertion of the assembly into the enlarged-part 41. In that event the hollow bore of the stem may be threaded for the insertion of a clamping stud for a terminal or a terminal lug may be clamped under the beaded edge of the stem. If desired, an insulating flanged ring may underlie the ring 59 to interpose a barrier between the central terminal and the shell or the ring 59. The interior of the shell is provided with a limited supply of triethanolamine. For a 35 ampere switch having an internal volume of the order of 21 cc. I provide a'mercury body of the order of 7 cc. and triethanolamine of the order of cc. The mercury that is employed is first treated as described in copending application, Serial No. 67,816, aforesaid.

The operation of the switch shown in Figure 12 is substantially as described in connection with Figures 6 to 11. The throat of the bore 58 is large because of the offsetting of the ceramic in the enlarged portion of the shell. The angle of the conical bore is made very low because of the freedom of travel of the mercury. This angle may be as low as 3 to 5. The deslderaturn is to determine the point; of break on the edge 5l-so as to secure accurate repeat performance. This requires an angle under 90. r

The surface of bore 50 need not be a true cone, but should be a surface of revolution so that the switch may be utilized in any angular position. A tapered surface at 58 on the spillway is desired for the accelerating effect on making and breaking. A substantially true cone is preferable, as I find that the action of approach and retreat is thereby made substantially uniform and more accurate repeat performance under various speeds of tilting is secured. The housing provides free runway for the traveling body of mercury 62.

It is therefore believed apparent that I have provided a switch possessing-the characteristic of repeat performance, provided by'the retention of a stable globule of mercury in contact with one electrode, and the provision of a sharp cutting edge over which the other body of mercury makes of lower amperage. The length of the enlarged portion of --the shell is reduced in this form of service because the ceramic i5 is extended into the bore of the'main shell portion 46. The forward end-left end in Figure 15-of the ceramic 15 terminates in a square end face 16 of less radial thickness than the height of the meniscus of mercury 62. Obviously the edgemight be brought down to a thinner section but I have found this to be less desirable because of the resultant weakness and consequent tendency to fracture both in manufacture and in use. The length of the spillway 58 in my switches is made great enough to-insure complete disconnection .i.e., an adequate gap for voltage to be impressed.

I prefer to make this distance generous, both for v the factor of safety in voltage and also to provide an adequate runway to accelerate the run of the movable body of mercury 62. I also aim to make the body of mercury v62 ample in length for two reasons, first to provide a large area of contact with the shell 46 when the two bodies of mercury 62 and 58 are united, and second to rests against a shoulder I8. The annular recessbetween annular shoulder 52 and the electrode 14 retains the stable body of mercury 58 as described above, particularly in connection with Figures 8 to 12. The ceramic l5 and electrode 14' are held in the soft rubber (natural or artificial) cup 65 which has the cylindrical portion 64, the

flange 66, and the back or bottom 61, Obviously the cup may, if desired, be divided but there is a distinct virtue in having a substantially imperforate envelope about the ceramic and the electrOde-in this and the other modifications so that any crack or joint in the ceramic or between the electrode and the ceramic is completely sealed against leakage electrically and mechanically.

' The backing plate 68 of Micarta, impregnated canvas, or the like, bears against the rear or bottom wall 61 of the rubber envelope 65.

A steel ring 69 fits inside the enlarged shell portion 41 and is in turn engaged-by the spun rim 16. The ring 69 and plate 68 are solidly pressed against therubber envelope to put the same under firm pressure and then the rim'is spun over as at 10. The electrode 14 has a sleeve projecting through the disc portion 61 of the rubber envelope 65 and the safety disc 68. This disc 68 is tough and will gradually deform under heat and pressure providing a highly desirable safety feature. The elasticity of the rubber envelope is useful in this connection as it will retaina seal of insulation though the safety disc and its electrode be outwardly displaced. It is to be noted in this connection that the electrode disc 14 is of a diameter not much less than that of the inner diameter of ring 69.

The stem 59 may be constructed as described in connection with Figure 12. I have shown a nut 68 and washer on stem 59. Thisnut and washer may be employed to draw the electrode 14 and safety disc 68 toward each other upon opposite sides of rubber disc 61 to' ensure a fluid-tight joint about stem 59. Although it is intended that sufficient pressure be placed upon the rubber en- -velope when the flange I0 is beaded over to accomplish a seal both about stem 59 and also at the joint. between the electrode I4 and ceramic 15. The electrode 14 may be constructed as shown in Figure 12 if desired.

The inside of the switch is cleaned, evacuated and filled as described in connection with Figure 12 with a suitable amount of cleaned and prepared mercury and a small amount of triethanolamine or like anhydrous viscous alkaline liquid. Hydrogen gas orcarbon monoxide or even city gas or any fixed hydrocarbon gas rich in hydrogen may be employed to fill the envelope.

The operation ofthe switch shown in Figure 15 is substantially the same as that shown in Figure 12.

It is to be observed however that.the mercury 62 must climb above the shoulder 16 before it flows up the spillway 5!! on the ceramic in the action of closing and on opening the mercury 62 runs off into the shell beyond the shoulder 16. Obviously the shell might be contracted in diameter beyond the shoulder 16 but this would reduce the width of the mercury body 62 and reduce the area of contact with shell 46.

In Figures 17 and 18 I have shown a modified form of switch when the two bodies of mercu y 811 and 82 are separated by a-tubular portion 83 of the ceramic 84. The ceramic 84 has an enlarged head portion 85 provided with shoulder 86.

Within the bore of the tubular ceramic is disposed the hollow electrode shell 81. wh ch is a closed end cylinder fitting closely in the bore. A stem 59, which may be of copper or the like. is welded, brazed or otherwise fixed to the outside wall of the bottom portion 88. (See F gure 19.) A flange either in the shape of a separate ring 89 attached by welding, brazing or the like. or in the shape of a folded flange 90 as shown in Figure 20 isreceived in a counterbore in the rear end of the ceramic to locate the electrode tube or cup 81 in the bore of the ceramic. The ball surface 92 of the bore serves as the breaking surface or gap between the two mercury to mercury contacts. The forward end of the tube 83 is preferably chamfered off to provide a sharp circular cutting edge 93 for parting the mercury bodies when they are merged. The main portion 94 of the envelope or shell which is preferably made of pure iron contains a body of mercury 80 which has a meniscus 95 at the end of the bore 92 rising up to form a substantially stable, i. e., completely curved top or meniscus portion so that a substantially stable form is maintained for all angles required for operation of the switch.

The enlarged portion 85 of the ceramic is encased in the soft rubber (natural or artificial) cup or envelope 65 having the cylindrical portion 64, the flange 66 and the bottom or disc portion 61. A Micartacanvas impregnated with a synthetic condensation product such as Bakelite-disc 68 overlies the rubber disc 61 and is pressed against the same to put the rubber under compression and is held by the steel retaining ring and flange Ill.

The shell has an enlarged portion 96 which has the forward shoulder 91 formed by beading in the junction of the main portion 94 and the enlarged ceramic retaining portion 96. Obviously the main portion 94 may be of the same diameter as the portion 96 .but a larger quantity of mercury will be required unless the ceramic is thickened along the portion 83.

The preparation for filling and the filling are as described in connection with Figure 12. A limited quantity of triethanolamine or equivalent liquid is employed.

The operation is as follows: Assume the switch is substantially level as shown. Sufficient downward tilt of the left hand end to start the mercury body 82 moving results in travel into engage- 81 and the shell 94. The cooling of the mercury in contact with the shell 94 both by direct contact and by the limited liquid fill is highly effec- Upon tilting in the opposite direction a part of the merged body of mercury begins to retreat into the bore 92 and inside the tubular electrode 81 until a point is reached where the tension of the body of mercury over the sharp annular edge 93 produces a break. Then the body 82 retreats over the bare part 92 of the bore thereby breaking the circuit. The break is sharp and decisive. The remaining meniscus 95 at the end of the tube 83 is stable and does not dribble. Excellent repeat performance is secured.

The switch operates at a very small angle and produces a rapid make and a rapid break due to the movement of both bodies of mercury. Heavy current can be carried by suitably proportioning of the parts. The size of the bore 92 with consequent control of the cross section of the connecting mercury governs the current carrying the inner surface of conical wall 48. The tendency of this construction is to cause a relative slippage of the porcelain insulator 49 with respect to rubber flange 66 when the device is assembled.

and the bead or flange i8 is rolled over to compress the parts. This results in a compression stress not only on the tapered surface 54 but also the cylindrical surface 53, as the rubber is quite soft and is easily distorted or deformed, particularly by slight amounts, although it is tough and resilient. The entire external periphery of the ceramic insert in Figure 12 and likewise the por-' tions confined within the enlarged portion of the shell in Figure 15 or 17 or any like switch may e made conical if desired. Likewise the enlarged shell portion need not be cylindrical, but may be made conical to conform to a similar shape of the ceramic.

While I have indicated that the free space in the envelope may be filled with hydrogen or other reducing gas, or alternatively with an inert gas such as helium, argon, etc., I wish to point out that, first, a gas filling of the envelope is not necessary. I may provide only a filling of ethanolamine vapor at less than atmospheric pressure, as disclosed in my copending application, Serial No. 745,842. Second, the liquid appears to make the use of hydrogen or the like unnecessary.

The ethanolamine as herein disclosed has many useful properties in this connection. It appears to have the ability to dissolve such slight coatings of dioxide of iron and of mercury as might result from any residual oxygen in the parts or in the vapor space. Thereby it renders hydrogen unnecessary. It appears to have valuable sealing properties in conjunction with the rubber gaskets, and it appears to seal off any pores or minute openings in the shell or its cooperating parts.

The use of a stable body of 'mercury is especially desirable in that a body of this size will retain its form, within limits, regardless of position; that is to say, a globule of less than twice meniscus curve size will remain unchanged in form even when moving down a polished vertical surface. In glass envelope switches it is impossible to use a stable -body of mercury of dimension, since the end of the glass tube is too close to the point of arc. This proximate arc causes the glass to spall and break. The present metallic envelope can take this arcing and not be damaged or changed.

I am aware that certain modifications of the invention herein disclosed will at once be apparent to those skilled in the art, and'I do not intend to limit my invention to the specific embodiments herein shown and described, nor to the specific details shown and described, except as recited in the appended claims, and I intend to claim the invention as broadly as it is novel over the prior art.

I claim:

1. In. a metallic envelope type of mercury switch, a pair of electrodes, one of said electrodes being disc-shaped, a ceramic having a spillway surface between said electrodes, said ceramic entirely supporting and defining with said one of said electrodes a retaining groove of a width not exceeding 3 a body of mercury in said groove in contact with said-oneelectrode, and an acutelyangled cutting edge between said body of mercury and said spillway surface.

2. A mercury switch comprising a pair of electrodes, one of said electrodes comprising a cylindrical metallic shell, 9. ceramic fixed in said shell adj acent the open end of said shell and supporting acute angle defined by a radially outwardly exand'spacing said other electrode within said open end of said shell, said ceramic defining with said other electrode an annular gg'oove of axial extent v such as to retain a body of mercury that will be 5 inherently stable-within the operating angle of said switch, and a sharp cutting edge formed by said ceramic and terminating an inclined runway between said stable body of mercury and a second body of mercury carried 'by said shell. I

3-,. In a metallic envelope typefof mercury switch, a pair of metallic electrodes; one of said electrodescomprising a circular disc, an annular spacing insert of ceramic material between said electrodes and having a tapered'spillway surface therebetween, said insert having an acute angle edge at the small end of said spillway surface and defining with said one of said electrodes an annular radially extending groove, said insert entirely supporting and spacing said electrode within said other electrode, a body of mercury in said groove of 'a size such that it retains its stability throughout the operating range of movement of said switch, and a second body of mercury in contact with said other electrode and capable or movement up and down said spillwayface leading from the interior of said shell, in electrode supported by and insulated frcm said,

shell by the outer end of said ceramic and defining with the small endroi said'surface an annular groove having anaxial extent not-substan- .in said envelope; for axially and radially comportion, a ceramic having a conical bore terminating in a sharp acute-angle annular shoulder,

till

pressing and fioatably supporting said frefracf tory therein.

8. A mercury switchof the metal envelope type having a refractory and an electrode forming with said refractory a i ecess spaced from said 20 envelope, elastic compressible sealing means holding said refracory and electrode in position with respect to said envelope, and a planar rigid compression disc engaging the radial face of saidi sealingmeans. I 25 9. A mercury switch of the metal envelope type having a ceramic insert provided with an axial passage theretlnough, an electrode closing the -.outer end of said passage; and resilient sealing 1 lar metallic shell closed at one end and having tially exceeding the length of two meniscus curves being inherently stable ,and rising radially inwardly 5.)! said ceramic above the edge defining; ,the inner end orsaid spillway surface, said other:

'body of mercury moving on said spillwagisurface into and .out or contact with'said stable bod} of mercury, and an acutely angiedcutting edge;

terminating the spillway side ot said groove whereby saidother body of'inerclll'y successively moves into andaiut of contact at said edge.

5. A mercuryiswitch comprising two electrodes spaced; apart by a ceramic member having an axiallysextending tapered passage theret'hrough, ,the larger end ot saidpassage terminating in 'one of said electrodes, the'otherof said electrodes comprising a disc or a'fdiameter smaller 5 than the external diameter or said insert, and the smaller end of said passage terminating in an 6. In combination, a] ferrous shell having a tubular contacting portion, a traveling body :of merc ary in ccntact therewith, an enlarged pertion forming a continuation or said contacting means supporting said elecfrode in axial abutting engagement with said insert to position and radially and axially cushion said insert within the envelope of said switch. 7

10. in a switch of the class described, a tubu;

an enlarged opening'at the other, and a rigid disc of insulation closing the open end, the margin of the open end being flanged over the edge of the disc, an electrode extending through said disc, a tubular ceramic supporting the electrode in one end thereof, and a body' 'of mercury in the shell. Z

11. Ihe combination of claim 10 with a rubber seal between the shell and the ceramic having radialiy inwardly extending portions at opposite ends of said ceramic. i

12. 'The combination of claim 10 with a rubber envelope embracing the outside surface of the ceramic and the rear face of said electrode for sealing the ceramic t j. ihe'electrode.

end'tubular 's'netallic shell having a main bore and having an extension of enlarged diameter open at its end, a closure of insulation for said open end, a ceramic having atapered conical bore disposed in said extension and having-the larger end or its conical boife substantially the same size as the main bore of the shell to provide a passageway for mercury} which passageway provides a maximum width-of mercury at the most constricted part of said bore, a body of mercury in the shell, a pocket for mercury being provided beyond the most cons'ricted part of j'the bore of the ceramic, and an electrode extending throughsaid closure and projecting contact with the mercury in said pocket, said electrode being of smaller diameter than said extension and said ceramic having an annular fiange between said extensi'cn and the periphery of said electrode. s

14.In ccmbination, in a-' mercury switch, a. bushing of refractory insulation having an internai; annular shoulder defining a wall of a mercury retaining pocket, a tapered bcre extendingfrom said shoulderto provide an insulating runway for mercury, a tubularr metal' shell provided 1 tive to the shell, an electrode having a face thereof forming a wall of said mercury pocket, a body of rubber forming a three-way seal between the shell, the bushing and the electrode, and means for confining said body of rubber under" compression.

15. An insulating body foruse in a mercury switch comprising a generally tubular body of refractory insulation comprising a substantially cylindrical peripheral portion, a gradually tapered intermediate portion, and'a sharply tapered end portion, the bore ofsaid body comprising a conical portion with its largest diameter adjacent said sharply tapered end portion, the

conical bore having a throat terminating in a sharp annular shoulder defined by a substantially radially extending surface for forming a parting edge for mercury.

16. The insulating body of claim 15 characterized further by a substantially cylindrical counterbore extending from said annular surface to v the end of the body.

17. For use in a mercury switch, an insulator and electrode assembly comprising the combination of a tubular body of refractory insulation having a conical internal surface extending from one end and terminating at its most restricted portion in a sharp shoulder defined by a substantially radially extending surface, an electrode disposed endwise in axial alinement with said body and in engagement therewith, said electrode and said body "defining between them, an annular groove for retaining a body of mercury in'contact with the electrode, the electrode having a stem portion, and an envelope of elastic insulation embracing the external surface of the body and of the electrode to seal the joint between said body and said electrode. 18. For use in a mercury switch, an insulator and electrode assembly comprising the combination of a tubular body of refractory insulation having a conical internal surface extending from one end and terminating at its most restricted portion in a sharp shoulder defined by a substantially radially extending surface, and an electrode disposed endwise in axial alinement with said body and in engagement therewith, said electrode and said body defining between them, an annular groove for retaining a body of mercury in contact with the electrode, said body of insulation having a tubular extension beyond the most restricted portion, and the electrode comprising a disc fitting within the tubular extension and having a flange overhanging the end of said extension.

19. In combination, a metallic switch envelope having an enlarged open end, a ceramic insert in said enlarged end, said insert having an axial K bore, an electrode carried by and insulated from said'enlarged end by said insert, a resilient cup receiving said insert and said electrode and pro viding an external annular and radial seal therefor, and a rigid insulating disc within the open end of said envelope for compressing said cup in sealing engagement between said enlarged end and said ceramic and, electrode.

20. In .a metallic envelope type of mercury switch including a cup-shaped metallic shell having an enlarged open end, a ceramic insert in said end having an external annular surface of smaller diameter than said end to'provide an annular gap therebetweenand having an axial bore, a discshaped electrode of smaller diameter than said insert surface supported solely by said insert for closing the outer end of said bore, a cup-shaped compressible gasket enveloping a portion of the annular surface of said insert and the outer radial surface of said electrode to fill said gap and enclose said electrode,'and a rigid planar disc member compressed axially against the radial face of said gasket;

21. A metallic mercury switch comprising a metallic cup-shaped shell having an enlarged open end, a ceramic insert in said end having an external annular surface of smaller diameter than said end to provide an annular gap therebetween, an electrode supported solely by said insert and having axial and radial seating engagement thereagainst, said insert forming an annular flange about the periphery of said electrode, and a resilient cup having a cylindrical flange filling said gap and having an integral planar base enclosing the end face of said ceramic flange and the rear face of said electrode.

22. A metallic mercury switch comprising a I metallic cup-shaped shell having anenlarged open end, a ceramic insert in said end having an external annular surface of smaller diameter than said end to provide an annular gap therebetween, an electrode supported solely by said insert and having axial and radial seating engagement therewith, said insert forming an annular flange about the periphery of said electrode, said electrode terminating within the axial limits of said insert and having a stud extending rearwardly therefrom, and resilient gasket means having a cylindrical flange filling said gap and having an integral planar base enclosing the end face of said ceramic flange and the rear face of said electrode and fitting closely about said stud.

23. A mercury switch comprising a metallic cup-shaped envelope having an enlarged end, a ceramic in said end having an axial bore, an electrode having radial and axial seating engagement in the outer end of said ceramic and having its periphery spaced from said envelope by said ceramic, resilient sealing means engaging said ceramic and electrode, a disc-like rigid insulating gasket for axially compressing said sealing means and an annular compression ring engaging said gasket and having an internal diameter such that it overhangs the periphery of said electrode.

24. A mercury switch comprising a metallic cup-shaped envelope having an enlarged open end, a ceramic in said end, a disc-shaped electrode having radial and-axial seating engagement in the outer end of said ceramic and having its periphery spaced from said envelope by said ceramic, resilient insulating compressible gasket means of high dielectric strength for cushioning said ceramic axially in said L envelope, a rigid planar insulating disc for axially compressing said gasket means, and a. metallic compression ring engaging the outer face of said disc and having an internal diameter such that it extends said insert at the smaller end of said internal surface, mercury in said envelope and a of.

velope having opposed external and internalfrusto-conical surfaces terminating at the small end of said frusto-conical section'of said envelope, awelectrode disc supported entirely by said insert 15 and spaced from the small end of the internal frusto-conical surface of said insert, and axially compressed sealing means radially compressing a portion of said insert and sealing the passage'between said shell and the external surface of said 20 insert.

27. For a mercury switch, a ceramic insert and' terminal structure comprising a cylindrical portion and a head portion, a tapered recess extending axially into the insert, an enlargement at the 25 small end of the tapered recess, the junction forming-a sharp annular shoulder, said insert having imperforate side walls, an axially disposed electrode extending into the enlargement,

and a stable body of mercury adapted to be 30 trapped in the enlargement by said shoulder and standing above the edge of said shoulder. 28. A switch comprising a cup-shaped metallic envelope having an enlarged openend, a ceramic bushing resiliently cushioned and sealed in said 35 end and having an axially extending recess, said recess comprising a frusto-conical raceway opening into said'envelope and terminating within said bushing in a radial shoulder, an electrode supported entirely by said bushing and spaced axially outwardly of said shoulder, an internal annular'wall in said bushing extending axially between said shoulder an'd-said last-named electrode and lying radially outwardly thereof, a body Y of mercury in the groove forward of said internal wall and extending radially inwardly beyond the defining edge between said raceway and said shoulder, a second body of mercury in continuous contact with said envelope and freely movable through said raceway and only partially filling the cross section of said raceway and said shoulder in switch closed position.

29. In a mercury switch, a sealed switch envelop'e comprising a metallic cup-shaped shell having a ceramic insert secured within the open end'thereof, an axially extending frusto-conical recess in said insert within said-shell, an electrode spacedfrom the smaller end of said recess, an annular groove formed by a radially extending wall at the small end of said recess and an enlarged annular axially extending wall. disposed I radially outwardly about said electrode, said electrode having a terminal extending axially outwardly of said insert externally of the open end. of said shell, a body of mercury retained in a portion of said groove in contact with said electrode, and a second body of mercury in'said shoulder movable into and out of engagement with said first body of mercury upon tilting of said en- PAUL s. BEAR.

' velope, I

DISCLAIMER 2,132,921.Paul 8'. Bear, Elkhart, Ind. SWITCH. Patent dated October 11, 1938. IIDiScIaimer filed April 2, 1940, by the assignee, Bucklen-Bear Laboratories,

nc. Hereby enters this disclaimer to claims 8 and 9 in said specification.

[Ojicial Gazette April 30, 1940.]

D l S C L A I M E R 2,132,92L-Paul 8'. Bear, Elkhart, Ind. SWITCH. Patent dated October 11, 1938. Disclaimer filed November 22, 1940, by e assignee, Bucklen-Bear Laboratorz'es, Inc.

Hereby enters this disclaimer to claim 29 in said specification.

[Ofiicial Gazette January 14, 1.941.] 

